Display apparatus with visual segment indicia

ABSTRACT

An apparatus for providing a visual display of encoded information on a cathode-ray tube screen wherein the information is stored in a memory which has a storage capacity greater than the display capacity of the tube screen. The address to the memory is decoded and in response to the writing of a preselected character row from the memory, and a selected scan line and scan line position, an indicia or marker signal is generated. Generation of the indicia signal occurs at a scan position adjacent the normal display area of the display screen. The signal serves to control the beam intensity of the cathode-ray tube so as to create a visual marker on the screen indicating the segment of the memory being displayed.

United States Patent Cook 1451 July 30, 1974 [54] DISPLAY APPARATUS WITHVISUAL 3,706,075 12/1972 Fredrickson et a1 340/1725 3,742,482 6/1973Albrecht et a1. 340/324 AD SEGMENT INDICIA [75] Inventor: Harold D.Cook, Wheaton, 111.

[73] Assignee: Teletype Corporation, Skokie, I11.

[22] Filed: Aug. 14, 1973 [21] Appl. No.: 388,296

[52] [1.5. CI 340/324 AD, 340/172.5 [51] Int. Cl. G06f 3/14 [58] Fieldof Search 340/324 AD, 172.5

[56] References Cited UNITED STATES PATENTS 3,082,294 3/1963 Dean 178/683,242,470 3/1966 Hagelbargcr et al. 340/172.5 3,422,420 1/1969 Clark340/324 AD 3,524,182 8/1970 Criscimagna ct a1. 340/324 A 3,610,902 /1971Rahenkamp et a1 340/172.5 3,643,252 8/1967 Roberts 340/324 A 3,654,6204/1972 Bartocci 340/l72.5 3,676,850 7/1972 Goldman ct al. 340/324 A3,680,077 7/1972 'Hobcrecht 340/324 A 3,683,359 8/1972 Kleinschnitz340/324 A Primary Examiner-David L. Trafton Attorney, Agent, oFirm-114M121?! 19 $.10 ELLE Landis 5 7] ABSTRACT An apparatus forproviding a visual display of encoded information on a cathode-ray tubescreen wherein the information is stored in a memory which has a storagecapacity greater than the display capacity of the tube screen. Theaddress to the memory is decoded and in response to the writing of apreselected character row from the memory, and a selected scan line andscan line position, an indicia or marker signal is generated. Generationof the indicia signal occurs at a scan position adjacent the normaldisplay area of the display screen. The signal serves to control thebeam intensity of the cathode-ray tube so as to create a visual markeron the screen indicating the segment of the memory being displayed.

Claims, 2 Drawing Figures 82 8O 78 UP 76 DOWN SCROLL RESET COUNTER 84OUTPUT [66 RESET LOAD ADDRESS 64 MEMORY ADDRESS MEMORY ADDRESS 68CHARACTER COUNTER 74 ROW COUNTER c1 oci COUNT 100 DIVIDER -c1 oc1 ROWRANDOM ACCESS DECODER MEMORY O E 56 HO K SCAN LINE FONT DECODER DECODER96 [I6 m [I4 m 112 f" 29 E0 ZN 6O 62 I26 124 PARALLEL TO T I SERIALSHIFT [O8 REGISTER L) K 104 I06 I02 PATENTED JUL 3 0 I 313 37.041

SHEET am 2 UP 76 DOWN SCROLL COUNTER" RESET 72 W OUTPUT /66, RESET LOADADDRESS 64 MEMORY ADDRESS MEMORY ADDRESS 68 CHARACTER COUNTER ROWCOUNTER -OLOOK COUNT IOO DIVIDER' CLOCK,

aa ROW I 85 v I RANDOM ACCESS DEOODER MEMORY ov m 44 E 94 3 v 5 R v 90//o \{T v v SCAN LINE FONT DECODER DECODER 9s 96 Z9 E, Z N 6O 2 I i JI22 T A I26 I24 T PARALLEL TO SERIAL HIFT REGISTER I08 CLOCK DISPLAYAPPARATUS WITI-I NISUAL SEGMENT INDICIA BACKGROUND This inventiongenerally relates to a display apparatus for providing a visualpresentation of encoded information and more particularly relates tosuch an apparatus which includes a memory having a capacity greater thanthe capacity of the display and means providing a visual indicia relatedto that segment of the memory being displayed.

Various systems have been suggested for providing a visual display ofstored, coded information. One such arrangement enters the informationinto a storage memory from which each coded character is selectivelyread-out, decoded and used to control the beam of a cathode-ray tube.Thus, the tube screen provides a visual presentation corresponding tothe character readout from the memory. The character presentation on thecathode-ray tube may be in the form of a dot matrix created by aplurality of horizontally spaced scans of the electron beam. The beam ispulsed during each scan to create the desired dot pattern.

When the number of character locations in the memory equals the numberof character locations on the screen of the cathode-ray tube, the memorycapacity is sufficient to fill the screen of the tube. If is oftendesirable to provide the memory with more capacity than the amountnecessary to fill the screen. Under such conditions, an entire messagecan be stored in the memory, however, only a portion of the text will bedisplayed at one time. The memory text is moved up or down past thewindow formed by the screen of the cathode-ray tube in a mannergenerally termed scrolling." During scrolling, the text material appearsto move vertically across the screen as though it was printed upon aroll of paper. Since the memory is capable of storing a greater numberof rows than are presented on the screen at any one time, it would beconvenient if the operator were provided with a visual indicator relatedto the particular portion or segment of the stored text being displayed.For example, let it be assumed that the cathode-ray tube screenaccommodates twenty-four rows of text, and that the memory capacity isequivalent to seventy-two rows of text. The operator would find ithelpful to be provided with some visual indication designating theidentity of row one, row twenty-five, and row forty-nine of the memorywhen displayed. An indicia or marker designating the first row of one ofthe three memory segments would always appear upon the screen thusproviding the user with a convenient reference indicating the segment ofthe memory being displayed and its relative position with respect to theremainder of the memory capacity.

It is particularly desirable if the memory segment markers. are placedupon the-cathode-ray tube screen at a location which is not utilized forthe display of information so that the full capacity of the cathode-raytube screen is available fortext material. Additionally, it alsoadvantageous if the segment markers are generated separate and apartfrom the memory rather than being stored therein. Such an arrangementallows the full capacity of the memory to be devoted to the storage oftext material.

SUMMARY OF THE INVENTION The illustrated embodiment'of' the inventionincludes a character display means in the form of a cathode-ray tube anda storage memory supplying information to the display. The storagecapacity of the memory exceeds the display capacity of the tube, thuspermitting only a segment of the display to be presented at a giventime. The memory segment is selected by an address means. Control meansresponsive to a selected address generates an indicia signal. Theembodiment further includes means actuated by the indicia signal forproducing visual segment indicia or markers on the display correspondingto the segment of the memory storage being displayed.

As illustrated the segment markers are placed upon the screen in an areaof the screen not generally used for text display, but rather adjacentthe text display area.

It is a main object of this invention to provide a display apparatusincluding means for indicating the segment of the storage memory beingdisplayed.

Other objects, advantages, and features of the invention will be morereadily appreciated after reference to the following description andaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates three fragmentarycathode-ray tube presentations and partial diagram of a portion of adisplay apparatus; and

FIG. 2 is a partial diagram which when combined with the diagram of FIG.1 illustrates a display apparatus including certain features of thisinvention.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT GENERAL Briefly, theillustrated embodiment generates indicia l0, l2, and 14 (FIG. 1) uponthe screen 15 of a cathode-ray tube 16 (FIG. 2) which provides the userwith a visual markers indicating the memory segment being displayed uponthe screen of the tube. A timing means 18 isillustrated in FIG. 1 whichsupplies the necessary timing signals and address outputs for control ofthe cathode-ray tube beam deflection circuits as well as the portion ofthe apparatus of FIG. 2. Encoded information is stored in a code storagememory 20 and selectively read-out for processing and control of thecathode-ray tube 16 which provides a visual display of the storedinformation. The capacity of the memory is greater than the displaycapacity of the screen of the cathode-ray tube 16.

The apparatus includes means for generating indicia upon the screenrelated to the segment of the memory storage being displayed. Each ofthe fragmentary views of FIG. 1 correspond to the upper left-hand comerof a screen raster displaying one memory segment. Three illustrativescreen fragments 22, 24, and 26 are shown which exhibit in sequencesegment indicia l0, l2, and 14 relating to a particular portion of thestorage memory. Although only three segment indicia are illustrated, itwill be appreciated that the concept may easily be expanded toaccommodate any number N of memory segments.

TIMING Throughout the following description, certain timingrelationships are described. These relationships are provided .to givethe reader a better understanding of the operation of the embodimentherein described and not in limitation of the invention. The letter E isillustrated to facilitate explanation and is formed by a matrix of dotsseven columns wide and nine lines high and the area of the rasterassigned to each character is nine dots wide and fourteen dots inheight. Serving to determine the spacing of the dots and establish attime base for the apparatus is a dot generator 28 which in turn drives acharacter width counter 30 of modulus nine, equivalent to the width ofthe raster alloted to a character. Upon the completion of the horizontalscan of each line of each character, the character width counter 30provides an output pulse the period of which is equivalent to the timenecessary to write the width of one character.

Providing an output pulse at the commencement of each horizontal scan ofthe cathode-ray tube, is a scan character counter 32 having a modulus ofone hundred including two divide by ten counters 34 and 36 in tandem. Anentire character line is scanned and the beam retraced during a timeduration equivalent to the generation of 100 characters. As illustrated,the width of the screen of the cathode-ray tube accommodates eightycharacters with a horizontal retrace time equivalent to 20 characters.Serving to trigger the horizontal retrace circuitry, a signal output issupplied by the scan character counter 32 and serves to trigger ahorizontal retrace circuit 38 which controls the horizontal deflectionof the cathode-ray beam after the 80th character in the row has beenscanned.

The count nine output of the first divide by ten decode 34 of the scancharacter counter 32 is fed to one input of a ninetynine count AND-gate40 and the count nine output of the second divide by ten decode 36 ofthe scan character counter 32 is fed to a second input of the AND-gate40. Thus, upon coincidence of the two count nine signals whichcorresponds to a count of 99, an output pulse is provided at the outputof the AND- gate 40 for purposes to be subsequently considered. It willbe appreciated that since the scan width of the screen is eightycharacters wide and the retrace time is approximately equivalent to 20characters, the ninetyninth pulse output will occur when the cathode-raybeam is at the left-hand side of the screen adjacent to the matrix areaassigned to the first character on the line. This portion of thehorizontal scan is generally non-linear and therefore, is usually notutilized for the generation of display characters. The output of thescan character counter 32 is fed to a scan line counter 42 with amodulus of fourteen. I

As previously mentioned, the matrix area assigned to each character isapproximately nine dots in width and fourteen dots in height. Thus, eachfourteen scans of the beam, correspond to the writing of an entirehorizontal row of characters. The scan line counter 42 generates oneoutput pulse for each fourteen scan lines. The counter levels in thescan line counter 42 are brought out via lines 44 for decoding purposesto be described. The output of the scan line counter 42 is fed to a textrow counter 46 modulus twenty-five. The vertical display area of thecathode-ray tube is of sufficient length to accommodate 24 rows ofcharacters; with the vertical retrace requiring a time equivalent to thewriting of one character tow. The output of the text line counter drivesa vertical retrace circuit 48.

MEMORY CONTROL With particular referece to FIG. 2, the storage memory 20is in the form of a random access memory. As previously mentioned, thecathode-ray tube 16 screen has a capacity sufiicient to display 24 rowsof characters. For purposes of discussion, the memory 20 is assumed tohave a storage capacity three times that of the display capacity of thecathode-ray tube screen or a memory capacity of 72 rows of characters.The memory 20 includes address inputs 50 and 52 and parallel outputlines 54 which feed the coded character signals to the input of a fontdecoder 56. The font decoder 56 serves to decode the information whichhas been stored in the memory 20 toa video format and includes anaddress 58 as well as output ports 60. The address input 58 of the fontdecoder 56 is connected by the lines 44 to the four parallel addresslevels provided by the scan line counter 42. The memory 20 presents aselected encoded character to the input of the font decoder 56, and theaddress lines 44, which present a binary level related to the scan line,select the appropriate decoding scan level for that character. Forexample, if an encoded letter E is presented to the font decoder 56 andthe address input designates scan line 6, the output will provide dotsat character columns 2 through 5 inclusive. The output of the fontdecoder is connected to the input of a parallel-to serial shift register62 which serves to convert the parallel to input from the font decoder56 into a serial output for control of the beam intensity of thecathode-ray display tube 16. The output from the register is stepped bypulses from the dot generator via line 63. Each output level of the fontdecoder 56 relates to one of the nine character columns.

Serving to address the memory 20 is a memory address character counter64 and a memory address row counter 66. The output of the charactercounter 64 and the output of the row counter 66 are connected to theinput address lines 52 and 50, respectively, of the memory. Thus, therow counter 66 addresses the memory with respect to the selected row ofcharacters and the character counter 64 serves to select the particularcharacter in that row. The display address character counter 64 isstepped by a clock pulse via line 68 from the output of the characterwidth counter 30 thereby causing the counter 64 to step once for eachcharacter width. Upon the lapse of a time interval equivalent to thescan time period of 100 characters, an output pulse is generated by thememory address character counter 64 which is applied to one input of areset OR-gate 70 via line 72 and to a divide by fourteen divider 74.After fourteen scan lines which is equivalent to the scanning of acomplete character row, the divide by fourteen divider 74 feeds a pulseto the clock input of the row counter 66. In response to this pulse, therow counter 66 is stepped one position, thereby addressing the memory 20to next adjacent character row. After a complete raster has beenscanned, the vertical retrace pulse from the output of the text rowcounter 46 is fed via line 76 to the load input of the row counter andto the remaining input of the OR-gate 70. Thus, the character counter 64is reset for each raster of characters as well as at the end of eachcharacter row. Additionally, upon the application of a vertical retracepulse to the load input of the row counter 66, the counter is loaded bythe address output of a scroll address counter 78.

The scroll counter 78 provides the address of the first row in thedisplay. For example, if the first 24 rows of the memory are to bedisplayed, the scroll counter will provide the address of the first row.If the second segment of the memory is to be displayed, the scrollcounter 78 will provide the address of the twenty-fifth row, andcorrespondingly, if the last segment is to be displayed, the scrollcounter 78 will provide the address of the forty-ninth row. Further, thedisplay may overlap any two memory segments. In such an instance, thescroll counter 78 will address an intermediate line, lt will beappreciated that regardless of the number of the first row displayed,the raster will always include the first row of a memory segment.Serving to increment the scroll counter 78 are two inputs 80 and 82respectively designated up and down. Additionally, a reset input 84 isprovided to reset the scroll counter 78 to the first row of the memory.The up, down, and reset inputs are controlled by external circuitrywhich does not form a part of this invention.

in operation, the scroll counter 78 is set to the first line to bedisplayed and in response to a vertical retracepulse via the line 76,the scroll address is loaded into the row counter 66. Thus, the memoryis addressed for the first row to be displayed and the first characterof the row. This character is read-out from the memory 20 and fed to thefont decoder 56. As previously mentioned, each row of characters iscomposed of fourteen scan lines, each of which defines a unique dotpattern. Assuming that the first character to be displayed is the letterE as illustrated in FIG. 1, the output of the front decoder 56 willprovide a dot at columns 2 through 8, corresponding to he first scanline of the row. This output is fed to the shift register 62 wherefromit is clocked serially into the intensity control element of thecathode-ray tube 16. After the completion of the scan of the firstcharacter, an output from the character width counter 30 steps thecharacter counter 64 one position to the second character in the row andthe memory 20 reads-out the second character of the line. The fontdecoder 56 provides an output related to the dot pattern of the firstscan line of the second character and the process continues until thefirst scan line of the first row of characters has been completed. Thecharacter counter 64 resets and commences scanning of the second scanline of the character row. Thus, each of the characters are decoded on aline by line basis until all fourteen scan lines comprising a singlecharacter row have been completed at which time the output of the divideby fourteen divider 74 supplies a pulse to the row counter 66 causing itto address the memory 20 at the second row. in this manner, the entireraster of 24 rows of characters are scanned and upon recurrence of thevertical retrace pulse, the memory address row counter 66 is againsloaded. In the event the scroll counter 78 has been incremented ordecremented, the display will start on the newly addressed row.

lNDlCIA GENERATION With further reference to FIG. 2, the illustratedembodiment includes a means for generating indica related to the memorysegment being displayed. A control means 85 is provided which generatesan indicia signal and includes an address row decoder 88, receiving theoutput of the row counter 66. The row decoder 88 generates an outputsignal in response to the occurrence of rows one, twenty-five, andforty-nine along lines 90, 92, and 94, respectively. As mentioned, thesecharacter rows designate the start of one of the three segments storedwithin the memory. The row one output of the decoder 88 is fed to oneinput of a first OR- gate 96 and the row twenty-five address counter isfed into one input of a second OR-gate 98. The row fortynine output isfed into the remaining inputs of each of the two OR-gates 96, and 98.Thus, each of the OR- gates supplies an output signal in response to amemory address corresponding to a forty-ninth memory row. The secondOR-gates 98 provides an output signal in response to row twenty-five andthe first OR-gate 96 provides an output signal upon the decoding of thefirst row address. The output from the OR-gate 98 is fed to one input,of a first AND-gate 102 and a second AND- gate 104. The output of theOR-gate 96 is fed to one input of a third AND-gate 106. Each of theAND-gates include three inputs. One input of each of the three AND-gates102, 104, and 106 is connected to the output of the ninety-nine countAND-gate 40 of the timing unit via line 108.

The decoding means additionally includes a scan line decoder 110, theaddress inputs of which are connected to the binary outputs of the scanline counter 42 via lines 44. The decoder 110 provides three outputs112, 114, and 116 corresponding to the respective decoding of scan linetwo, scan line six, and scan line ten of each character row. The scanline two output 112 is connected to the remaining input of the AND-gate102, the scan line six output is connected to the remaining input of theAND-gate 106, and the scan line ten output is connected to the remaininginput of the AND- gate 104. Thus, upon the simultaneous occurrence ofcharacter row one, scan line six, and the ninety-nine count signals, theAND-gate 106 will provide an output pulse to one input of an OR-gate118. Upon the simultaneous occurrence of scan lines two or ten withcount ninety-nine and character row twenty-five, the AND- gates 102 and104 provide output pulses which are respectively coupled to the tworemaining inputs of the OR-gate 118. In response to scan lines two orsix or ten with character row forty-nine, and scan count ninetynine, allthree of the AND-gates 102, 104, and 106 will sequentially provideoutput pulses to the inputs of OR- gate 118. Thus, it will beappreciated that in response to a display of character row one whichcorresponds to the first segment of the memory, the AND-gate 106 willprovide an output only during a small portion of the scan of line six.When character line twenty-five is addressed, which is the first row ofthe second segment of the memory, the AND-gate 102 will provide anoutput corresponding to the occurrence of scan line two and the AND-gate104 will provide an output corresponding to he occurrence of scan lineten. In response to the address of character row forty-nine from thememory, all three of the dot AND-gates 102, 104, and 106 willsequentially provide an output corresponding to the occurrence of scanlines two, six, and ten coinciding with the output pulse from the countninetynine AND-gate 40. The output of the OR-gate 118 is connected tothe anodes of two steering diodes 120 and 122 the cathodes of which areconnected to inputs 124 and 126 of the parallel to serial shift registercorresponding to character columns six and seven.

For purposes of discussion, let it be assumed that the first twenty-fourlines of memory are being displayed on the face of the cathode-ray tube16 and the memory 166. During the retrace of the cathode-ray beam at a 7point just prior to the commencement of the scanning of the firstcharacter, a ninety-nine count pulse occurs at the remaining input tothe AND-gate 1106 creating an output signal. As previously mentioned,this signal occurs during a non-linear portion of the scan at a screenposition not generally used for display purposes and is coupled throughthe OR-gate 118 and the steering diodes 120 and 122 to the inputs 124and 126 of the parallel to serial shift register 62. Thus dots aregenerated at scan line six, columns six and seven. Since'this portion ofthe scan is non-linear, the two generated are compressed producing asingle elongated dot as illustrated at Id in FIG. I.

When the scroll counter 78 has loaded the row counter 66 for the secondsegment of display commencing at row twenty-five of the memory an outputpulse appears at the output of the OR-gate 98. Upon coincidence with theoutput from the decoder 110 corresponding the scan lines two or ten andthe output of the ninety-nine AND-gate 40, an indicia signal is suppliedto the sixth and seventh column inputs I24 and 126 of the shift register62. A second segment indicia 12 is produced in the form of two elongateddots in the left margin of the display at scan lines two and ten asillustrated in FIG. 1. In a similar manner, during the display of thelast segment of the storage memory 20, line forth-nine will be decodedalong with scan lines two, six, and ten to produce the third segmentindicia 14 consisting of three dots at the left of the display area.Thus, it will be appreciated that the display of lines one, twenty-five,and forty-nine will each produce a unique dot display at the left marginof the display area adjacent the first character row of the memorysegment. In this manner, the user is provided with visual indiciarepresenting the particular segment of the storage memory beingdisplayed. The location on the screen of these segment indicia isparticularly convenient as they are readily recognizable by the operatorsince they are located in the left margin of the display adjacent thetext. It will be appreciated that the generation of these segmentindicators does not utilize any storage memory capacity, therebyallowing the entire memory to be devoted to the storage of information.Further, the segment indicators are not displayed upon a portion of thedisplay area which is generally used for the display of characterinformation, but rather, during that portion of the scan line which isnon-linear. Thus, the indicators do not reduce the available displaycapacity of the apparatus.

OPERATION Briefly, in response to the operators command, the scrollcounter 78 is set with the address of the first line to be displayed.Upon command of the vertical retrace signal 76, the scroll address isloaded into the memory row counter 66 and the character counter 64 isreset. 6

intensity of the beam of the cathoderay tube 16. The.

row address to the memory and the scan line of the character row aredecoded. Upon coincidence of the first character row and a selected scanline, a signal is generated which is pulsed to the control circuitry inresponse to the ninety-ninth pulse output from the scan charactercounter 32. The occurrence of the ninetyninth pulse is such that theindicia signal occurs when the scan line is located to the left of thenormal text area on the tube screen, creating a unique dot patterncorresponding to the memory segment being displayed.

Although the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood thatvarious changes in form and detail may be made without departing fromthe spirit and scope of the invention.

What is claimed is:

1. In a display apparatus including character display means and astorage memory supplying information to the display means for visualpresentation thereon, the memory having a storage capacity exceeding thedisplay capacity of the display means, the improvement comprising:

address means for selecting a segment of the total capacity of thestorage memory for display, control means responsive to said addressmeans for generating an indicia signal related to that segment of thecode storage being displayed, and means actuated by said indicia signalfor producing visual segment indicia on the display means correspondingto the segment of the memory storage being displayed.

2. The apparatus of claim 1 wherein said control means includes decodingmeans responsive to said memory address means so as to generate saidindicia signal upon the occurrence of a preselected address.

3. In the display apparatus of claim 2, wherein the display meansincludes a cathode-ray tube, the information from the memory is fed to afont decoder serving to decode the output of the memory storage into adisplay format, and scan line address means are provided for controllingthe font decoder, the improvement further comprising:

said control means for generating the indicia signal receiving theoutput of the scan address and serving to generate said indicia signalto control the cathode-ray tube display at a time determined by saidscan line address means.

4. The apparatus of claim 3 wherein said scan address means includes ascan signal generator controlling the horizontal scan circuitry of thecathode-ray tube, said scan signal generator supplying a scan positionsignal to said control means indicating a scan line position locatedadjacent the normal display area of the cathoderay tube; said controlmeans generating said indicia signal in response to said scan positionsignal so as to place said signal segment indicia upon the cathode-raytube screen at a preselected location not used for the normal display ofinformation.

5. The apparatus of claim 4 wherein:

the character format displayed upon the cathode-ray tube screen is inthe form of a dot matrix, each character being composed of a pluralityof horizontal scan lines producing a predetermined number of dots toform the desired character;

said indicia producing means including means for selectively generatingat least one dot upon the cathode-ray tube in response to said indiciasignal thereby providing an indication of the storage segment beingdisplayed.

6. The apparatus of claim wherein said control means includes gatingmeans controlled by said memory address decoding means and said fontdecoder for generating N number of dots wherein N corresponds to therelative position of the memory segment being displayed with respect tothe memory capacity.

7. The apparatus of claim 5 wherein said control means is responsive tosaid scan position signal prior to the start of the generation of a scanline so as to place said indicia adjacent the normal text display areaof the cathode-ray tube.

8. The apparatus of claim 2, wherein the display means includes acathode-ray tube, ascan signal generator for controlling the horizontalretrace circuitry of the cathode-ray tube, said scan signal generatorsupplying a signal to said control means indicating a scan line positionlocated adjacent the normal display area of the cathode-ray tube so asto place said segment indicia upon the cathode-ray tube display surfaceat a location not used for the normal display of information.

9. The apparatus of claim 8 wherein said control means is responsive tosaid scan signal generator adjacent the start of the normal display areaof the cathoderay tube.

10. The apparatus of claim 2 wherein said memory address means includesa row address for addressing the memory to a selected row;

said decoding means is responsive to said row address so as to generatesaid indicia signal upon the occurrence of a preselected row therebyproviding an indicia on the display means corresponding to a selectedrow of the memory segment being displayed.

11. The apparatus f claim 10 wherein said row address is in the form ofa presetable counter and a scroll counter for selectively presettingsaid row address in response to a control signal.

12. In the display apparatus of claim 11, wherein the display meansincludes a cathode-ray tube and the information from the memory is fedto a font decoder serving to decode the output of the memory storageinto a display format and scan address means controlling the fontdecoder, the improvement further comprising:

said control means receiving the output of the scan address and servingto generate said indicia signal to control the cathode-ray tube displayat a time determined by said scan line address means.

13. The apparatus of claim 12 wherein said scan address means includes ascan signal generator controlling the horizontal scan circuitry of thecathode-ray tube, said scan signal generator supplying a scan positionsignal to said control means indicating a predetermined scan lineposition located adjacent the normal display area of the cathode-raytube; said control means generating said indica signal in response tosaid scan position signal so as to place said visual segment indiciaupon the cathode-ray tube screen at a preselected location not used forthe normal display of information.

14. The apparatus of claim 13 wherein:

the character format displayed upon the cathode-ray tube screen is inthe form of a dot matrix, each character being composedof a plurality ofhorizontal scan lines producing a predetermined number of dots to formthe desired character;

said indicia producing means includes means for selectively generatingat least one dot upon the oath ode-ray tube in response to said indiciasignal thereby providing an indication of the storage segment beingdisplayed.

15. The apparatus of claim 14 wherein said dot generating means isresponsive to said scan positions signal prior to the start of thegeneration of a scan line so as to place said indicia adjacent thenormal text display area of the cathode-ray tube.

1. In a display apparatus including character display means and astorage memory supplying information to the display means for visualpresentation thereon, the memory having a storage capacity exceeding thedisplay capacity of the display means, the improvement comprising:address means for selecting a segment of the total capacity of thestorage memory for display, control means responsive to said addressmeans for generating an indicia signal related to that segment of thecode storage being displayed, and means actuated by said indicia signalfor producing visual segment indicia on the display means correspondingto the segment of the memory storage being displayed.
 2. The apparatusof claim 1 wherein said control means includes decoding means responsiveto said memory address means so as to generate said indicia signal uponthe occurrence of a preselected address.
 3. In the display apparatus ofclaim 2, wherein the display means includes a cathode-ray tube, theinformation from the memory is fed to a font decoder serving to decodethe output of the memory storage into a display format, and scan lineaddress means are provided for controlling the font decoder, theimprovement further comprising: said control means for generating theindicia signal receiving the output of the scan address and serving togenerate said indicia signal to control the cathode-ray tube display ata time determined by said scan line address means.
 4. The apparatus ofclaim 3 wherein said scan address means includes a scan signal generatorcontrolling the horizontal scan circuitry of the cathode-ray tube, saidscan signal generator suPplying a scan position signal to said controlmeans indicating a scan line position located adjacent the normaldisplay area of the cathode-ray tube; said control means generating saidindicia signal in response to said scan position signal so as to placesaid signal segment indicia upon the cathode-ray tube screen at apreselected location not used for the normal display of information. 5.The apparatus of claim 4 wherein: the character format displayed uponthe cathode-ray tube screen is in the form of a dot matrix, eachcharacter being composed of a plurality of horizontal scan linesproducing a predetermined number of dots to form the desired character;said indicia producing means including means for selectively generatingat least one dot upon the cathode-ray tube in response to said indiciasignal thereby providing an indication of the storage segment beingdisplayed.
 6. The apparatus of claim 5 wherein said control meansincludes gating means controlled by said memory address decoding meansand said font decoder for generating ''''N'''' number of dots wherein Ncorresponds to the relative position of the memory segment beingdisplayed with respect to the memory capacity.
 7. The apparatus of claim5 wherein said control means is responsive to said scan position signalprior to the start of the generation of a scan line so as to place saidindicia adjacent the normal text display area of the cathode-ray tube.8. The apparatus of claim 2, wherein the display means includes acathode-ray tube, a scan signal generator for controlling the horizontalretrace circuitry of the cathode-ray tube, said scan signal generatorsupplying a signal to said control means indicating a scan line positionlocated adjacent the normal display area of the cathode-ray tube so asto place said segment indicia upon the cathode-ray tube display surfaceat a location not used for the normal display of information.
 9. Theapparatus of claim 8 wherein said control means is responsive to saidscan signal generator adjacent the start of the normal display area ofthe cathode-ray tube.
 10. The apparatus of claim 2 wherein said memoryaddress means includes a row address for addressing the memory to aselected row; said decoding means is responsive to said row address soas to generate said indicia signal upon the occurrence of a preselectedrow thereby providing an indicia on the display means corresponding to aselected row of the memory segment being displayed.
 11. The apparatus fclaim 10 wherein said row address is in the form of a presetable counterand a scroll counter for selectively presetting said row address inresponse to a control signal.
 12. In the display apparatus of claim 11,wherein the display means includes a cathode-ray tube and theinformation from the memory is fed to a font decoder serving to decodethe output of the memory storage into a display format and scan addressmeans controlling the font decoder, the improvement further comprising:said control means receiving the output of the scan address and servingto generate said indicia signal to control the cathode-ray tube displayat a time determined by said scan line address means.
 13. The apparatusof claim 12 wherein said scan address means includes a scan signalgenerator controlling the horizontal scan circuitry of the cathode-raytube, said scan signal generator supplying a scan position signal tosaid control means indicating a predetermined scan line position locatedadjacent the normal display area of the cathode-ray tube; said controlmeans generating said indica signal in response to said scan positionsignal so as to place said visual segment indicia upon the cathode-raytube screen at a preselected location not used for the normal display ofinformation.
 14. The apparatus of claim 13 wherein: the character formatdisplayed upon the cathode-ray tube screen is in the form of a dotmatrix, each character being composed of a plurality of horizontal scanlinEs producing a predetermined number of dots to form the desiredcharacter; said indicia producing means includes means for selectivelygenerating at least one dot upon the cathode-ray tube in response tosaid indicia signal thereby providing an indication of the storagesegment being displayed.
 15. The apparatus of claim 14 wherein said dotgenerating means is responsive to said scan positions signal prior tothe start of the generation of a scan line so as to place said indiciaadjacent the normal text display area of the cathode-ray tube.